The invention relates generally to machine condition monitoring. More particularly, the invention relates to a phase signal capture during an anomaly in operation of a machine or sensor.
In the field of machinery diagnostics and protection, a sensor signal that has an output signal related to the machine speed is required. Typically, the sensor signal is a pulse signal generated once-per-event from a projecting key or a notch on a moving element of the machine such as a rotating shaft. In the case of a rotating shaft, a notch passing the sensor once-per-turn triggers the sensor. The once-per-turn event is useful not only for determining the shaft speed but also to provide a phase reference for comparing against other shaft sensor signals. For example, the phase difference between the phase reference and a radial vibration transducer signal provides an indicator of machine condition.
Currently, when there is a problem with the triggering of the sensor signal, an oscilloscope is connected to the buffered output of the sensor and used to evaluate the problem. If the problem is intermittent, then the oscilloscope has to be left connected to the monitoring system to attempt to capture a reoccurrence of the problem.